SARS-CoV-2 infects the human kidney and drives fibrosis in kidney organoids.

Kidney failure is frequently observed during and after COVID-19, but it remains elusive whether this is a direct effect of the virus. Here, we report that SARS-CoV-2 directly infects kidney cells and is associated with increased tubule-interstitial kidney fibrosis in patient autopsy samples. To study direct effects of the virus on the kidney independent of systemic effects of COVID-19, we infected human-induced pluripotent stem-cell-derived kidney organoids with SARS-CoV-2.

Gitelman-Like Syndrome Caused by Pathogenic Variants in mtDNA.

Background: Gitelman syndrome is the most frequent hereditary salt-losing tubulopathy characterized by hypokalemic alkalosis and hypomagnesemia. Gitelman syndrome is caused by biallelic pathogenic variants in encoding the Na-Cl cotransporter (NCC) expressed in the distal convoluted tubule. Pathogenic variants of , , , or may result in the same renal phenotype of Gitelman syndrome, as they can lead to reduced NCC activity.

Quantitative assessment of inflammatory infiltrates in kidney transplant biopsies using multiplex tyramide signal amplification and deep learning.

Delayed graft function (DGF) is a strong risk factor for development of interstitial fibrosis and tubular atrophy (IFTA) in kidney transplants. Quantitative assessment of inflammatory infiltrates in kidney biopsies of DGF patients can reveal predictive markers for IFTA development. In this study, we combined multiplex tyramide signal amplification (mTSA) and convolutional neural networks (CNNs) to assess the inflammatory microenvironment in kidney biopsies of DGF patients (n = 22) taken at 6 weeks post-transplantation.

Renal amyloidosis: validation of a proposed histological scoring system in an independent cohort.

Background: In systemic amyloidosis, the kidney is frequently affected and renal involvement has a major impact on survival. Renal involvement is clinically characterized by decreased estimated glomerular filtration rate (eGFR) and proteinuria. The two most common renal amyloidosis types are light chain-related amyloidosis (AL) and serum amyloid A (AA) amyloidosis.

Functional tests to guide management in an adult with loss of function of type-1 angiotensin II receptor.

Background: Genetic loss of function of AGT (angiotensinogen), REN (renin), ACE (angiotensin-converting enzyme), or AGTR1 (type-1 angiotensin II receptor) leads to renal tubular dysgenesis (RTD). This syndrome is almost invariably lethal. Most surviving patients reach stage 5 chronic kidney disease at a young age.

Histopathological examination of removed kidney allografts: Is it useful? A retrospective cohort study.

The incidence and relevance of histological findings in removed allografts is unknown. In this study, we investigated the outcome of routine histopathological examination of removed allografts. We performed a retrospective cohort study in patients with kidney graft failure ≥3 months after transplantation.

Treatment-resistant nephrotic syndrome in dense deposit disease: complement-mediated glomerular capillary wall injury?

Background: The C3 glomerulopathies (C3G) are recently defined glomerular diseases, attributed to abnormal complement regulation. Dense deposit disease (DDD) is part of the spectrum of C3G, characterized by electron-dense deposits in the lamina densa of the glomerular basement membrane. Patients with DDD present with hematuria, variable degrees of proteinuria, and kidney dysfunction.

Deep Learning-Based Histopathologic Assessment of Kidney Tissue.

Background: The development of deep neural networks is facilitating more advanced digital analysis of histopathologic images. We trained a convolutional neural network for multiclass segmentation of digitized kidney tissue sections stained with periodic acid-Schiff (PAS).

Methods: We trained the network using multiclass annotations from 40 whole-slide images of stained kidney transplant biopsies and applied it to four independent data sets.

Nivolumab-associated Nephrotic Syndrome in a Patient With Renal Cell Carcinoma: A Case Report.

Introduction: Immune checkpoint inhibitors have taken an important place in the treatment of different types of malignancies. These drugs are known to have specific immune-mediated adverse events. We describe a case of severe nephrotic syndrome secondary to treatment with nivolumab in a patient with renal cell carcinoma.

Absence of Intragraft B Cells in Rejection Biopsies After Rituximab Induction Therapy: Consequences for Clinical Outcome.

Background: The pathophysiological role of intragraft B cells during renal allograft rejection is unclear.

Methods: We studied B-cell infiltration during acute rejection in 53 patients who participated in a clinical trial in which adult renal transplant patients were randomized between a single intraoperative dose of rituximab (375 mg/m) or placebo as induction therapy. Two independent pathologists scored all biopsies in a blinded fashion according to the Banff classification and scored for the presence of B cells and plasma cells using CD79a and CD138 as markers.

The Dutch Transplantation in Vasculitis (DUTRAVAS) Study: Outcome of Renal Transplantation in Antineutrophil Cytoplasmic Antibody-associated Glomerulonephritis.

Background: Data on the outcome of renal transplantation in antineutrophil cytoplasmic antibody-associated glomerulonephritis (AAGN) patients are still limited. In particular, how disease recurrence in the renal allograft defines graft outcome is largely unknown. Therefore, we conducted a multicenter observational clinical and histopathological study to establish recurrence rate of AAGN in the allograft and the impact of recurrence on allograft survival.

Ciliopathies with skeletal anomalies and renal insufficiency due to mutations in the IFT-A gene WDR19.

A subset of ciliopathies, including Sensenbrenner, Jeune, and short-rib polydactyly syndromes are characterized by skeletal anomalies accompanied by multiorgan defects such as chronic renal failure and retinitis pigmentosa. Through exome sequencing we identified compound heterozygous mutations in WDR19 in a Norwegian family with Sensenbrenner syndrome. In a Dutch family with the clinically overlapping Jeune syndrome, a homozygous missense mutation in the same gene was found.

High urinary excretion of kidney injury molecule-1 is an independent predictor of end-stage renal disease in patients with IgA nephropathy.

Background: The variable course of immunoglobulin A nephropathy (IgAN) warrants accurate tools for the prediction of progression. Urinary kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are markers for the detection of early tubular damage caused by various renal conditions. We evaluated the prognostic value of these markers in patients with IgAN.

The tetraspanin CD37 protects against glomerular IgA deposition and renal pathology.

The tetraspanin protein CD37 is a leukocyte-specific transmembrane protein that is highly expressed on B cells. CD37-deficient (CD37(-/-)) mice exhibit a 15-fold increased level of immunoglobulin A (IgA) in serum and elevated numbers of IgA+ plasma cells in lymphoid organs. Here, we report that CD37(-/-) mice spontaneously develop renal pathology with characteristics of human IgA nephropathy.

Podocyte foot process effacement as a diagnostic tool in focal segmental glomerulosclerosis.

Podocyte foot process effacement is characteristic of proteinuric renal diseases. In minimal change nephrotic syndrome (MCNS) foot processes are diffusely effaced whereas the extent of effacement varies in focal segmental glomerulosclerosis (FSGS). Here we measured foot process effacement in FSGS and compared it to that in MCNS and in normal kidneys.

Urinary excretion of fatty acid-binding proteins in idiopathic membranous nephropathy.

Background: It is suggested that proteinuria contributes to progressive renal failure by inducing tubular cell injury. The site of injury is unknown. Most studies have used markers of proximal tubular cell damage.

Interobserver agreement of scoring of histopathological characteristics and classification of lupus nephritis.

Background: Assessing renal biopsies from patients with lupus nephritis (LN) is a difficult task and it is subject to interobserver variability. In this study the interobserver agreement amongst five nephropathologists was analysed.

Methods: Five specialized nephropathologists scored 126 biopsies, comprising 87 first and 39 repeat biopsies from 87 patients with biopsy-proven proliferative LN, included in a randomized controlled trial.

Pathological variants of focal segmental glomerulosclerosis in an adult Dutch population--epidemiology and outcome.

Background: A working group has defined five subtypes of focal segmental glomerulosclerosis (FSGS) based on light microscopic assessment (Columbia classification). Limited information is available on the prognostic and therapeutic implications of this classification in a European population. We conducted a retrospective analysis in 93 adult patients with biopsy-proven FSGS to determine the clinical features and outcome of FSGS variants.

Treatment with cyclophosphamide delays the progression of chronic lesions more effectively than does treatment with azathioprine plus methylprednisolone in patients with proliferative lupus nephritis.

Objective: To analyze the effect of treatment with either pulse cyclophosphamide (CYC) or azathioprine (AZA) combined with methylprednisolone (MP), on serial biopsy results in patients with proliferative lupus nephritis, and to evaluate the predictive value of various histopathologic and clinical parameters with regard to disease outcome.

Methods: Biopsy specimens from patients with proliferative lupus nephritis, obtained at study entry and after 2 years of therapy, were scored according to a standardized method, and results assessed in relation to disease outcome.

Results: Of the 87 patients originally enrolled, 39 underwent repeat biopsy.

Angiotensin converting enzyme inhibition prevents development of collapsing focal segmental glomerulosclerosis in Thy-1.1 transgenic mice.

Background: Thy-1.1 transgenic mice develop hypercellular focal and segmental glomerulosclerosis (FSGS) lesions that mimic human collapsing FSGS, in 7 days after injection with anti-Thy-1.1 antibodies.

Expression and effect of inhibition of aminopeptidase-A during nephrogenesis.

Aminopeptidase-A (APA) is a metalloprotease that cleaves N-terminal aspartyl and glutamyl residues from peptides. Its best-known substrate is angiotensin II (Ang II), the most active compound of the renin-angiotensin system (RAS). The RAS is involved in renal development.

The parietal epithelial cell: a key player in the pathogenesis of focal segmental glomerulosclerosis in Thy-1.1 transgenic mice.

Focal segmental glomerulosclerosis (FSGS) is a hallmark of progressive renal disease. Podocyte injury and loss have been proposed as the critical events that lead to FSGS. In the present study, the authors have examined the development of FSGS in Thy-1.